Triplet wide-angle objective lens



SEARCH ROOM 8 m L E V N C mw B 0 RE m 3E m T m P m T 3 6 9 1 0 3 M A v 6 D y Filed Dec. 8, 1959 INVENTORS CARLBAUR FRIEDBERT FREITAG United States Patent Office 3,087,384 Patented Apr. 30, 1963 erably being capable of focusing by means ofiiio'vemens j its front component. S---- w A lens ma e 1 c'tTr'dance with this invention incorporates a positive meniscus disposed on the object side of the lens which is made of glass having a refractive index for the d-line of the line of the spectrum greater than 1.675. It also incorporates a biconvex lens disposed on the image side of the objective and a biconcave lens disposed between the two aforementioned lenses having one surface which is considerably more curved than the other and being arranged with its surface of lesser curvature facing the meniscus.

Triplet lens systems have been used in many diiferent configurations; however, they are rarely used as wide-angle objectives. An object of this invention is to provide a wide-angle objective incorporating only three lenses having a medium aperture ratio and being capable of focusing by movement of the front lens. It unexpectedly provides an image which is not inferior to those provided by wide-angle objectives having a greater number of lenses or components, but it is less expensive and easier to fabricate than those multilens objectives.

In accordance with this invention, a triplet wide-angle photographic objective of the type described is provided by arranging the surface refractive power of the second surface as well as the third surface to have absolute values which are not less than the reciprocal of 4.5 times the focal length of the objective and not more In accordance with another characteristic of this invention, the second axial air spacing, I is not less than 2.5 times and not greater than 4 times the first axial air spacing, 1 in accordance with the following formula:

251 4 41, In addition, the sum of all the lens thicknesses of the objective 3 E 1 'y=l is not less than 3 times and not greater than 10 times the first axial air spacing, 1 in accordance with the follow- 65 ing formula:

3 3l;$2d,510l1 Furthermore, the ratio of the arithmetic sums of the surface refractive powers of the positive meniscus to the corresponding values of the biconvex lens is not less than 1.4 and not greater than 1.9 in accordance with the following formula:

L an R5 R2 Its/@319 R5 Re For obtaining a wide angle of view, it is important that the positijglens disposed adjacent the object has a strongly defined meniscus form while the negative lens incorporates a third surface which is decidedly weak relative to those of ordinary three lens systems. F urthermore, it is important in focusing by movement of the front lens that the refractive power of this front lens is made relatively strong, and correspondingly the first axial air spacing be made relatively small. To provide a favorable marginal brightness for the relatively large diameter first and last lenses, the examples display relatively great lens thicknesses which also facilitate their manufacture.

Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawing wherein similar reference characters refer to similar parts and in which the single figure is a schematic representation of an embodiment of this invention with the radii of curvature being represented by R R the axial lens thicknesses being represented by d d and the axial air spacings being represented by 1 1 In the following examples of this invention and in the drawing, the construc tional factors are progressively numbered proceeding in a direction toward the image plane, the refractive indices of the glasses, n n refer to the n -line of the spectrum (587.6 mi), and the Abbe numbers or dispersive powers are represented by v v and v Example I [Aperture ratio 114.5. Angle of view 58-00.

Focal length I Lens Glass Thickness Refractive Dispcrsive Radius or Axial Index n Power :1

Separation d1=5.9 TZ4I=L7I3O fl1=53. 9 R==+l60.0

li=2. 9 R3=1T6.0

dg=2. 0 '7lr1z=l. 6166 02 36. 6 R 23.1

d3=5.7 Tld'=l 6385 91 55 5 Rs=- S1. 5

Example [I [Aperture ratio 1:4.0. Angle of view 5860. Focal length f=100] Lens Glass Thickness Refractive Dispersive Radius 0r Axial Index na Power 0 Separation d1=7.5 fld1= 1.7440 L 44.9 Rg=+ 251.0

l1= 2.6 Ra= 154.0

liz= 2.0 naz= 1. 6990 1)} 30.0 R4=+ 27.0

d 5.5 Tldt= 1.7440 zn= 44.9 R 78.2

Example Ill [Aperture ratio 1:3.5. Angle of view 5860. Focal lenght /=100] Lens Glass Thickness Refractive Disperslve Radius or Axial Index 11.; Power Separation d 8.5 nd1= 1.788 vi= 50.4 Rg=+ 165.0

li= 3.7 R 175.0

d1= 2.0 7ld2= 1.6502 v= 33.7 Rl=+ 29.1

lz=l0.0 R 151.0

d 6.0 71:13: 1.7130 v3= 53.9 R 84.4

R (2) Not more than 20.03 in lens thicknesses and axial air spacings; (3) Not more than i0.03 in refractive indices with reference to the d-line of the spectrum; and

(4) Not more than *-5 units in v-values.

What is claimed is: 1. A photographic wide-angle objective lens having three components of medium aperture ratiojbeing capable of focusing by moyemengof its front componengtsaid objective lens comprising a meniscus OFBtiSitiYLrefrac. tive power disposed on the object side of said objective lens, a biconvcx component disposed on the image side ofsaid objective lens and a biconcave component disposed between said meniscus and said bicO n v x lens, and having numerical data with all constructional factors progressively numbered proceeding in a direction toward the image plane substantially as follows:

[Aperture ratio 1:4.5. Angle 01' view 5860. Focal length f=l00] to the d-line of the spectrum, and v v represent the dispersive powers.

2. A photographic wide-angle objective lens having three components of medium aperture ratio being capable of focusing by movement of its front component, said objective lens comprising a meniscus of positive refractive power disposed on the object side of said objective lens, a biconvex component disposed on the image side of said objective lens and a biconcave component disposed between said meniscus and said biconvex lens, and having numerical data with all constructional factors progressively numbered proceeding in a direction toward the image plane substantially as follows:

[Aperture ratio 124.0. Angle of view 5860. Focal lengtlif=] Lens Glass Thickness or Axial Separation Refractive Dispersive Index 12.

Radius Power 1;

TLd3=1. 7440 in which:

R R represent the radii of curvature, d d represent the axial thicknesses of the lenses, l l represent the axial air spacings, n n g represent the refractive indices relative to the d-line of the spectrum, and v v represent the dispersive'powers.

3. A photographic wide-angle objective lens having three components of medium aperture ratio being capable of focusing by movement of its front component, said objective lens comprising a meniscus of positive refractive power disposed on the object side of said objective lens, a biconvex component disposed on the image side of said objective lens and a biconcave component disposed between said meniscus and said biconvex lens, and having numerical data with all constructional factors progressively numbered proceeding in a direction toward the image plane substantially as follows:

[Aperture ratio 123.5. Angle of view 5860. Focal length /'=100] Lens Glass Thickness Refractive Disperslve Radius or Axial Index nu Power :2

Separation dr- 8.5 7Ld1=1.7884 01=50.4 Rz=+165.0

z,= 3.7 R =l75.0

d .0 Tlaz=l. 6502 n=33.7 Rl=+ 29.1

l=10.0 R =+l5l.0

d3= 6.0 fla3=1.7130 E3=53.9 R4= 84.4

in which:

R R represent the radii of curvature, d d represent the axial thicknesses of the lenses, l l represent the axial air spacings, mi, 12 represent the refractive indices relative to the d-line of the spectrum, and v v represent the dispersive powers.

References Cited in the file of this patent UNITED STATES PATENTS 1,987,878 Tronnier Ian. 15, 1935 2,279,372 Herzberger Apr. 14, 1942 2,446,402 Aklin Aug. 3, 1948 2,818,777 Hudson et al. Jan. 7, 1958 2,966,825 Baur et al. Jan. 3, 1961 

1. A PHOTOGRAPHIC WIDE-ANGLE OBJECTIVE LENS HAVING THREE COMPONENTS OF MEDIUM APERTURE RATIO BEING CAPABLE OF FOCUSING BY MOVEMENT OF ITS FRONT COMPONENT, SAID OBJECTIVE LENS COMPRISING A MENISCUS OF POSITIVE REFRACTIVE POWER DISPOSED ON THE OBJECT SIDE OF SAID OBJECTIVE LENS, A BICONVEX COMPONENT DISPOSED ON THE IMAGE SIDE OF SAID OBJECTIVE LENS AND A BICONCAVE COMPONENT DISPOSED BETWEEN SAID MENISCUS AND SAID BICONVEX LENS, AND HAVING NUMERICAL DATA WITH ALL CONSTRUCTIONAL FACTORS PROGRESSIVELY NUMBERED PROCEEDING IN A DIRECTION TOWARD THE IMAGE PLANE SUBSTANTIALLY AS FOLLOWS: 